The present invention relates to a switchable antenna for the VHF and UHF frequency bands, intended in particular for aircraft.
Numerous aircraft, and especially military jet airplane, have to incorporate at one and the same time antennae for transmission and reception in the VHF band, in particular from 100 to 156 MHz, and in the UHF band, in particular from 225 to 400 MHz. For reasons especially of weight, it would be desirable to be able to use, for this application, one single transmitting and receiving antenna switchable between the two bands, VHF and UHF. The practical realisation of such a switchable antenna comes up against various problems, resulting more particularly from the large bandwidth and the long range required for the antenna.
In particular, the realisation of a passive antenna that is switchable between the VHF and UHF bands is not practicable, because of the large bandwidth to be covered. Nor is it practicable to use, for the application under consideration, an antenna adapted with lossy elements because such an antenna would offer too limited a range.